cathode-ray tube

The Columbia Encyclopedia, 6th ed.

Copyright The Columbia University Press

cathode-ray tube, special-purpose electron tube in which electrons are accelerated by high-voltage anodes, formed into a beam by focusing electrodes, and projected toward a phosphorescent screen that forms one face of the tube. The beam of electrons leaves a bright spot wherever it strikes the phosphor screen. To form a display, or image, on the screen, the electron beam is deflected in the vertical and horizontal directions either by the electrostatic effect of electrodes within the tube or by magnetic fields produced by coils located around the neck of the tube. Some cathode-ray tubes can produce multiple beams of electrons and have phosphor screens that are capable of displaying more than one color. Cathode-ray tubes are used in television sets, computer monitors, automated teller machines, oscilloscopes, and radar displays.

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cathode-ray tube

cathode-ray tube Evacuated electron tube used for television picture tubes, oscilloscopes and display screens in radar sets and computers. An electron gun shoots a beam of electrons, focused by a grid. The electrons strike a fluorescent screen and produce a spot of light. In a television tube, an electrostatic or magnetic field deflects the beam so that it scans a number of lines on the screen, controlled by the incoming picture signals.

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cathode ray

cathode ray Radiation emitted by the cathode of a thermionic electron valve containing a gas at low pressure. In 1897 J. J. Thomson identified the rays as streams of charged, elementary particles having extremely low mass, later called electrons. Some electrons are emitted because the cathode is heated but most because of collisions between the cathode and positive ions formed in the valve.

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